good question -- I don't think the astra jab is available any longer . It never got approval in the US may be the reason .
Pfizer has been re labelled 'comirnaty' and Moderna now known as 'spikevax' Whether they are the same as the original is anyone's guess, even the manufacturers .
Don't forget the boosters will be required to maintain your status as available to work -- not yet but very soon. Also, the new variant omicron which has essentially put the already vaccinated back to square one , with implication that the current crop of vaccines is useless against it.